Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof withtransitional graphical user interface showing my new design in a firststate; and,

FIG. 2 is a front view thereof in a second state.

The broken lines in the figures depict environmental subject matter andform no part of the claimed design. The outermost broken lines in thefigures show a display screen or portion thereof and form no part of theclaimed design. The appearance of the animated user interfacesequentially transitions between the images shown in FIGS. 1-2. Theprocess or period in which one image transitions to another forms nopart of the claimed design.

CLAIM I claim the ornamental design for the display screen or portionthereof with transitional graphical user interface, as shown anddescribed.